Industrial safety requires protection of operators, maintenance personnel, and bystanders from potential injuries from hazardous machinery or materials. In many cases, the hazards can be reduced by automatically sounding an alarm or shutting off a process when dangerous circumstances are sensed, such as by detection of an operator approaching or entering an area proximate the hazardous machinery or materials.
In some instances, industrial safety is required in such areas, hereinafter referred to as safety areas, where materials and/or products are continuously or periodically transported, such as on conveyors. To provide safety in such instances, various types of systems are known for distinguishing between the presence of such conveyed materials and operators, which employ vertical and/or horizontal light curtains. In such systems, generally, upon detection of materials moving through the safety area, the light curtains are muted.
Such known systems suffer numerous drawbacks which compromise the safety and/or reliability of the systems. For example, if an undesired object, such as an operator, enters a safety area along side entering materials as the light curtain is muted, the system may not detect the presence of the undesired object. As a result, an operator may enter into the hazardous area without triggering an alarm or equipment shut down.